“…3.In women,the deformity of knee joint was associated with backward pelvis and straightening of lumbar curvature(P<0.01),while in men, the deviation of lower limb weight axis was associated with forward pelvis(P<0.01).The difference was not signi cant in severe group(P>0.05).The reason may be that women's pelvis is relatively wide in shape, but shorter and the tension of the surrounding muscle ligaments,such as the iliolumbar ligament,is relaxed compared with that of men,resulting in different changes in pelvis backward,resulting in reduced lumbar curvature and reduced interluminal space of the knee joint [12] .Previous studies have con rmed that female LL has a positive correlation with PI,and as LL decreases, PI decreases because the line of force compensates.Katsumi et alsuggested that the reduction of lumbar lordosis in knee osteoarthritis is a compensation for knee exion contracture [13] .Sagittal alignment is not limited to the lumbar spine,but involves a complex interplay of hip,pelvic,and spinal alignment.When the lumbar lordosis Angle decreases,in order to maintain standing balance,there will be pelvic tilt,rotation,and multiple surface imbalance.Differences in Sagittal radiography parameters caused by genders is described in Fig. 4.For example,Vigdorchik et alfound that 204 cases (41%) of 500 patients with hip osteoarthritis had Low back pain, which may be caused by compensatory pelvic rotation in hip osteoarthritis,which may change the normal line of force of lumbar spine and induce low back pain [14] .However, the male pelvis is generally narrow and deep,and its line of force transmission is easy to affect the lower limb weightbearing axis,such as the femur side deformity of the male hip joint with acetabular syndrome,which damages the glenoid margin and articular cartilage [15] . At the same time,our study also found that there was a positive correlation between male SS and LPFA.When the weight bearing axis of male lower limbs deviated from the midpoint of the knee joint,the pelvis would tilt forward due to compensation.This compensation may be due to tension in the abdominal muscles and increased tension in the iliopsoas muscle,which causes the anterior rotation during hip exion,hip abduction,and natural pull on the pelvis,causing the body's weight to shift forward.…”